This invention relates to the field of shopping carts, and more specifically to a system for detecting a load placed on the lower tray of a shopping cart and signaling a checkout clerk of its presence.
Individuals operating supermarkets and shopping centers have long been faced with the problem of customers mistakenly or intentionally leaving items on the lower tray of their shopping carts, obscured from the view of a checkout clerk by the checkout counter. Many items are removed from stores in this manner without being paid for, and the resulting monetary losses are quite significant.
Consequently, several systems have been devised to signal a checkout clerk of the presence of a parcel on the lower tray of a shopping cart as that cart is wheeled through the checkout line.
U.S. Pat. No. 3,051,936 discloses an alarm system for shopping carts wherein a load placed on the lower tray of a shopping cart completes an electrical circuit running from a voltage source to a conductive portion of the floor on which the shopping cart is rolled, in turn to the shopping cart and back from the shopping cart to a second conductive portion of the floor insulated from the first conductive portion, to a signaling device and finally back to the voltage source. This system is very complex, and requires adaptation of the shopping carts and the floor passing through the checkout line. These modifications are both time consuming and expensive, and limit later renovation or reorganization of the store. Because the system must detect the very low currents required to prevent injury to customers, and must itself have a relatively low resistance, false alarms created by wet shoes or metallic objects are a continuing problem. Finally, the system is subject to frequent failure due to loss of electrical contact between the cart and the conductive portions of the floor caused by the buildup of dirt, waxes, or other substances.
U.S. Pat. No. 3,263,774 discloses a control apparatus which forces a checkout clerk to lean over the counter to depress a switch before operating the cash register, and in so doing necessarily place themself in a position to observe the lower tray of the shopping cart, which is illuminated by a light when that switch is depressed. This system is very inconvenient for the operator, and represents more of a nuisance to the checkout clerk than an aid to efficiently checking a customer's purchases.
U.S. Pat. No. 3,457,423 discloses a radiation sensitive detection system for shopping carts using an array of light beams and photoelectric cells connected to a logic circuit which discriminates between a shopping cart, a load on the lower tray of the shopping cart, and the legs of the customer as they pass through the checkout line. To be effective, the array of light beams and electric eyes must be carefully aligned, and while relatively expensive and complicated to install, this system is still prone to failure and false signals for several reasons: customers often move back and forth in line when placing items on the checkout counter or reaching for a product displayed near the checkout counter, more than one person or a person with small children may pass through the checkout line at one time, or a person may go through the line without a shopping cart. Furthermore, in this system a different array of light beams must be arranged for each type of shopping cart used and the appropriate logic circuit designed for that array--tasks which are too complex and impractical for field installers to perform.
U.S. Pat. No. 4,327,819 discloses an object detection system for a shopping cart having a reflector mounted on a spring-loaded, pivoting bracket which supports the lower tray of a shopping cart. When a load is placed on the lower tray of the shopping cart. When a load is placed on the lower tray of the shopping cart, the tray pivots down and depresses the spring-loaded bracket, which in turn moves the reflector into line with a light beam and photoelectric cell, thus completing an electrical circuit and activating a signal for the checkout clerk. The use of a single electric eye and a reflector mounted on the cart tray do reduce some of the problems inherent in those systems using an array of light beams to discriminate cart, load, and customer. However, the spring-loaded, pivoting bracket assembly is different and time consuming to install, prone to jamming or wedging, and its placement at the rear of the cart makes the entire system easy to circumvent. The electric eye or reflector may also be blocked by a person's leg, or covered by an unscrupulous customer, and the shiny surface of certain metallic cart frames may cause false signals. A person may also break the reflector off the tray. Furthermore, because the reflector only passes the light beam and electric eye for a brief moment, the signal must be held and displayed until the clerk notices it, and resets the circuit by closing a reset switch.
The shopping cart with lower tray signaling device disclosed in my parent application Ser. No. 06/645,056 presents several advantages over prior designs in that the spring means for elevating the lower tray are positioned adjacent the pivotal axis of the tray near the front of the cart, and no portion of the tray need be vertically disposed over the cart frame at the rear of the cart, so that there is no mechanism to jam, and the tray cannot be wedged in the upright position. Furthermore, the one-piece spring means may be easily manufactured and quickly installed, using a single tool to mount the spring means and reflector on the cart. This system does have some of the same limitations as the previous designs, however, in that the reflector or electric eye may be blocked or obscured by a customer, the electric eye and reflector must be carefully aligned with the light beam, and the system requires resetting.
Therefore, one object of this invention is to design a detection system for loads placed on the lower tray of a shopping cart which does not require aligning a light beam, reflector, and photoelectric cell, which cannot be covered or blocked by a customer, and which is resistant to tampering.
A further object of this invention is to design the above detection system so that it may be easily mounted on existing shopping carts and installed in checkout lines presently in use.
A further object of this invention is to design the above detection system so that in operation it is unobserved by the customer.
Still another object of this invention is to design the above detection system so that it may operate completely automatically, without requiring activation or resetting by the checkout clerk.
U.S. Pat. No. 4,591,175 discloses a shopping cart antitheft apparatus for preventing the removal of shopping carts from the vicinity surrounding a shopping center. The device comprises a locking mechanism which locks the caster wheel of the shopping cart once it is rolled over a magnetic barrier embedded around the perimeter of the shopping center, so that the cart will only travel in circles and cannot be stolen.
Such an apparatus would not function to detect loads placed on the lower tray of a shopping cart, nor provide a signal to the checkout clerk that the load has not been removed from the tray.
In a distinct field of art, U.S. Pat. No. 3,778,808 discloses an electronic weight monitor for use in vehicle weight scales having a spring loaded platform on which increasing loads are placed, and a reed switch which is moved into contact with a magnet once a predetermined amount of weight has been placed on the platform, thus activating the reed switch and closing a signal circuit. While such an electric weight monitor could be installed on the lower tray of a shopping cart, some method of linking the electric circuit on the weight monitor to a signal circuit having a display visible to the clerk at the checkout counter would be necessary. Furthermore, a self-contained voltage supply would be required within the weight monitor on the shopping cart, which would likely require the frequent replacement of batteries or the use of many expensive fuel cells.